1. Field of the Invention
This invention generally relates to a method and apparatus for the separation of components combined in a fluid mixture. More specifically, a fluid mixture is introduced to a sorption zone of a rotating sorption bed which is contained within a plurality of manifolds. A portion of the separated fluid exiting the sorption zone of the rotating sorption bed is used to cool the sorbent in a cooling zone and subsequently heated to desorb the sorbed fluid to regenerate the sorption material for reuse. The method and apparatus of the present invention is highly effective in the removal of components from both liquids and gases and does not require the use of valves for passing the fluid from one processing zone to the next.
2. State of the Art
Fluid purifications/separations are required in many areas. Industrial chemical processing requires many separations which require the concentration of a contaminant into a smaller fluid stream. Sorption processes have long been used to purify fluid streams. Most sorption is conducted in batch processes or cyclic processes. Other continuous sorption processes such as the one described in U.S. Pat. No. 4,522,726 require large distribution valves which significantly add to the volume of the system.
Other fluid purification requirements include air purification for chemical defense. In this instance, the requirement is for the air to be cleaned of chemical warfare contaminants prior to air entering a collective protection shelter for military personnel. Presently, U.S. chemical defense is based on the use of Whetlerized activated carbon. This activated carbon is made by impregnating a coal based charcoal, which has been steam activated, with copper, chromate and silver ions dissolved in an ammonium solution. The metal ions are used to chemisorb blood agents such as cyanogen chloride (CK) and hydrogen cyanide (AC). Some of the blood agents, virtually all of the blister agents (such as distilled mustard (HD) and Lewisite (L)), and virtually all of the nerve agents (such as Sarin (GB) and Soman (GD)) are physically adsorbed in the activated carbon. A major problem with Whetlerite activated charcoal is that it is not reusable due to: (1) once a blood agent has been chemisorbed on a metallic ion, the sorption site is now filled and may not be made available to another molecule or agent and (2) the metal ions lower the ignition temperature of the activated carbon to a point where the blister and nerve agents may not be desorbed by thermal regeneration in a reasonable time without igniting the carbon. Thus, the most significant problem associated with Whetlerite is the logistic burden it places on the military supply system, due to its nonregenerability. Whetlerite filters require replacement every year (every two months in hot, humid climates) during peach time. In war time, they must be replaced before each blood agent attack and immediately after each blood agent attack.
The second major problem with Whetlerite is the loss of its CK efficacy due to high humidity and/or high temperature. In one week of aging, Whetlerite filters lose 40% of their CK life. After one year, the CK life of a Whetlerite filter may be only 25% of its initial life. Severe storage conditions can reduce the CK effective capacity of 18% of the initial CK life. In addition to the loss of CK life due to sorption of water vapor, Whetlerite filters lose capacity by sorbing other organic vapors which would be found on the battlefield. ASC/TEDA Whetlerite mitigates some of these problems but still loses capacity with exposure to humidity.
Finally, the Whetlerite canisters are dangerous to replace, particularly when they are inside a vehicle; there is no practical way to determine the residual life left in a Whetlerite filter; and the Whetlerite filters require the use of a costly impregnation process which about doubles the cost of the carbon.
To be able to ascertain the practical alternative to Whetlerite, various potential technologies have been evaluated. Catalytic oxidation, chemical decomposition, combustion, thermal decomposition, corona discharge, laser decomposition, microwave decomposition, cold trap, high pressure adsorption, membrane separation, pressure swing adsorption (PSA), temperature swing adsorption (TSA), combined PSA/TSA and regenerative closed loop life support systems were reviewed. The TSA was selected as the most viable alternative technology, as well as the most mature technology in various studies performed.
The above techniques all have various problems associated with their implementation. For example, the TSA system has a large volume requirement that would affect the size of the vehicle's cargo capacity. Also, these systems have relatively large power requirements that may interfere with the effective operation of the vehicle. Therefore, a more volume efficient, energy efficient system is required to make regenerable filtration more attractive for use on military vehicles and the like.
Other devices and methods for purifying fluid steams on a continuous basis have also been disclosed in the art. For example, U.S. Pat. No. 4,391,616 discloses a rotating canister dehumidifier that contains a carbon fiber filter and provides simultaneous radial and axial flow of air through the filter.
U.S. Pat. Nos. 3,780,498 and 3,883,320 disclose a continuous system for the removal of sulfur oxides from waste gas steams. This system contains two rotating beds where one bed serves as a heat exchanger to recover the useful heat from the waste gas stream and a second rotating bed serves to effect the removal of sulfur oxides from the gas stream.
In U.S. Pat. No. 2,617,986, an apparatus for treating liquids or gases is disclosed that comprises a rotatable annular drum containing conical baffles and tapered passageways.
U.S. Pat. No. 3,197,944 discloses a rotary absorber for gases, particularly nitrogen. While a rotary device is disclosed, the movement is intermittent as opposed to continuous.
U.S. Pat. No. 4,046,525 discloses a method for separating harmful components from a fluid steam which comprises at least two adsorptive units. Both units contain a plurality of cylindrical or bag-shaped adsorptive elements that are made of a cloth-like or sheet-like adsorptive material. Desoprtion is achieved by a heated purging gas jetting device.
U.S. Pat. No. 4,522,726, a liquid separation system is disclosed. Discrete fluid steams are introduced into individual treatment sections of the disclosed device where fluid flow is in both directions.
U.S. Pat. No. 4,595,575 discloses the chemisorption of gaseous pollutants Pollutants are washed out by a technique where the waste gas passes through the bed in codirectional or counter current flow to the wash liquid.
U.S. Pat. No. 4,574,874 discloses a chemisorption thermosystem that provides a cooling output by revolving an array of thermal elements through heat sink and heat source temperature zones. This system is disclosed as being useful for a vehicle air conditioning system.
U.S. Pat. No. 4,589,892 discloses a dehumidifying apparatus that includes a sequenced fed carousel containing a plurality of axial modular desiccant beds.
U.S. Pat. Nos. 4,548,802 and 4,599,225 disclose continuous flow separation apparatus that includes alternating sorption and desorption zones.
It would nevertheless be desirable if the regeneration air desorption of a particular sorption material utilized in a purification system would not require a separate clean stream source for this regeneration. Furthermore, it would be highly desirable for the sorption material to have a relatively long life time even though it is in continuous operation. It would furthermore be advantageous if the system would operate not only on a continuous basis, but could do so without frequent interchange of critical elements, e.g., without interchange of used sorption material and the like. None of the foregoing disclosures teach nor suggest such a device or system.